From: Lin Ming <mlin@ss.pku.edu.cn>
Subject: Re: [RFC PATCH] xen: get correct nr_irqs_gsi value from hypervisor
Date: Tue, 10 Apr 2012 23:16:35 +0800
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Cc: xen-devel@lists.xensource.com, x86@kernel.org, Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>, Ingo Molnar <mingo@redhat.com>, Xiantao Zhang <xiantao.zhang@intel.com>
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On Tue, 2012-04-10 at 22:57 +0800, Lin Ming wrote:
> nr_irqs_gsi is set in probe_nr_irqs_gsi()
> 	nr_irqs_gsi = gsi_top + NR_IRQS_LEGACY;
> 
> gsi_top is set in mp_register_ioapic()
> 	gsi_top = gsi_cfg->gsi_end + 1;
> 
> mp_register_ioapic() calls io_apic_read, which don't have a Xen specific
> version. Actually, io_apic_read() always return -1 on Xen Dom0 kernel.
> 
> So currently, nr_irqs_gsi is always wrong on Xen Dom0 kernel.
> 
> This patch gets the correct nr_irqs_gsi value from Xen hypervisor with a
> hypercall.
> 
> Signed-off-by: Lin Ming <mlin@ss.pku.edu.cn>
> --
>  arch/x86/include/asm/io_apic.h  |    2 ++
>  arch/x86/kernel/apic/io_apic.c  |    2 +-
>  arch/x86/xen/setup.c            |    9 +++++++++
>  include/xen/interface/physdev.h |    6 ++++++
>  4 files changed, 18 insertions(+), 1 deletions(-)
> 
> (I will send xen hypervisor patch in another mail)\

Here is xen hypervisor side patch:

[RFC PATCH] x86: Add a new physdev_op PHYSDEVOP_nr_irqs_gsi
http://marc.info/?l=xen-devel&m=133407101003891&w=2

Regards,
Lin Ming